THE mother of a prolific activist told an inquest into her son’s death from a drug overdose that his paranoia over state surveillance was “exacerbated and heightened” by undercover police officers who infiltrated protests.

Tom Palmer, 28, who was a “leading light” in the Occupy movement and had been living in a camp near Camden Lock, had been sectioned under the Mental Health Act, with doctors concerned about his fixation on MI5 and police spies, Poplar Coroner’s Court heard on Tuesday. But Mr Palmer did not believe he was unwell and his mother, Judith, told the court that the well-documented deployment of police spies, posing as fellow activists, had “hindered his recovery”.

“During the Occupy Movement which began in 2011 Tom undoubtedly came into contact with plain-clothed and undercover officers,” she said.

“From that time he was heavily involved in activism in London and talked about many other such encounters. And although his perceptions of reality were often blurred and unfocused, his paranoia was exacerbated and heightened because it was based on a truth that has been very well documented.

“His recovery was hindered because there were many reminders in the press that such things do happen, and not all of his suspicions were delusional.”

Mr Palmer, sometimes known as “Kingfisher”, split his time between his parents’ home in Staffordshire and living with friends and in squats in London, the court heard. He had been a part of some of the most high-profile protests in recent years, taking a key role in the takeovers by the Occupy London movement at St Paul’s Cathedral and Finsbury Square. The public gallery was packed with around 20 friends and fellow activists.

Ms Palmer told the court that her son had refused to take anti-psychotic medication prescribed by doctors, adding: “I think he tried to self-medicate with drinking and some drugs.”

In the weeks before his death he had been campaigning against Wetherspoon’s plans to expand the Ice Wharf pub’s beer garden on public land next to the canal in Camden Town.

The coroner heard concerns about the care Mr Palmer received from mental health services and problems exchanging information between different trusts.

Mr Palmer had been awaiting trial for criminal damage after urinating on Thames House, the headquarters of MI5 in Millbank on July 4.

His mother said: “There was an incident at the MI5 building. Tom very deliberately got himself arrested for that because he wanted his day in court, so he could come to court with all the evidence he had.”

She said he had at times been fearful of the security services, adding: "He said to me 'mum, if I die you will investigate my death, won't you?'”

The court heard that Mr Palmer had been smoking crack-cocaine and snorting lines of heroin at a friend’s house in Hoxton on the night before he died last August.

Daniel Phythian, who was with him, said: “I just got the impression that he wasn’t really used to these drugs.” Asked if he believed his friend had a mental illness, he said: “I just thought he had a very bizarre, surreal, incredible sense of humour that people took a bit too seriously at times.”

Asked to describe his friend, Mr Phythian said: “So generous, funny, strange, every adjective I can think of, no negative ones though. I think he just hated injustice in the world.”

Mr Palmer was found unresponsive the following morning, on August 22. Paramedics spent nearly an hour-and-a-half attempting to revive him.

Assistant coroner Sarah Bourke gave the cause of death as “acute heroin toxicity, in a background of recent alcohol use”.

In her formal determination, she recorded that “Tom was concerned at the role of surveillance in the protest movement”.